Chone sp.

Giangrande, Adriana & Licciano, Margherita, 2006, The genus Euchone (Polychaeta, Sabellidae) in the Mediterranean Sea, addition of two new species and discussion on some closely related taxa, Journal of Natural History 40 (21 - 22), pp. 1301-1330 : 1316-1319

Chone sp.

( Figures 8 , 9 )

as Oriopsis armandi in Castelli (1982).

Material examined

Twenty specimens from Follonica (Tyrrhenian sea), 6 m depth on sand bottom, 1981, PCZL; eight specimens , Ligurian Sea (Zoagli), 10 m depth on sand bottom, 1990, PCZL; two specimens , Adriatic Sea (Brindisi), 0.5 m depth, 1989, on detritic hard bottom, PCZL; two specimens Fiumicino (Tyrrhenian sea), 25 m depth, 1991 on muddy sand, PCZL .

Description

Small worm with eight thoracic and 10 abdominal chaetigers ( Figure 8A ). Total branchial crown length 1 mm. Total thorax–abdomen length 2.5 mm, maximum width 0.4 mm at chaetiger 7. Branchial lobe each with four fully developed radioles; feather-duster structure with numerous paired pinnules. Palmate membrane present for about half of the radiolar length ( Figure 8E ). Outer surface of radioles slightly rounded. Radiolar flanges present. Sub-distal ends of radioles long filiform ( Figure 8E ). Radiolar eyes absent. Dorsal lips pointed, longer than wide ( Figure 8D ), dorsal radiolar appendages not detected. Ventral lip not detected. Ventral margin of anterior peristomial ring as triangular lobe ( Figure 8B ), extending slightly beyond the collar. Peristomial collar membranous, well developed with narrow dorsal gap ( Figure 8B ), ventral margin slightly higher than dorsal ( Figure 8C ). Collar margin entire. Notopodial fascicles with six elongate narrowly hooded chaetae in chaetiger 1. Chaetigers 2–8 with superior elongate narrowly hooded chaetae, three to four per fascicle ( Figure 8H ); inferior notochaetae arranged as four bayonet-type anteriorly and four to five posterior short and broadly hooded chaetae ( Figure 8I , 9A ); neuropodial acicular uncini in chaetigers 1–8 with a short and blunt main fang surmounted by a series of small teeth starting in profile very deeply ( Figures 8F , 9B ), eight uncini per torus. Abdominal neuropodia each with single transverse row of four narrowly hooded chaetae. Abdominal notopodia with uncini rasp-shaped, rectangular, and with teeth of equal size over a poorly developed main fang not extending beyond breast, last abdominal chaetigers with uncini showing a more developed dentate region ( Figure 8G ), 13–15 uncini per torus showing intratorus variation ( Figure 9D ). Pygidium rounded with long cirrus ( Figure 8A ). Eggs in the thorax. Tube unknown.

Remarks

Chone sp. is distinguished from all the other Chone species in having thoracic uncini type 2 ( Figure 7B ). In this feature it is more similar to Amphicorina genus (type 4, Figure 7D ), from which, however, it is distinguished for several other features such as the organization of the branchial crown (snowflakes in Amphicorina ) and the presence of only two types of thoracic chaetae in Amphicorina . As already stated, thoracic uncini type 2, very similar to those present in Chone sp. , can be found in some small Euchone species (Chiade sensu Cochrane), which are clearly distinguishable from Chone sp. in having an Amphicorina -like organization of the branchial crown (snowflake) and the presence of the anal depression.

All the other features of the here-described Mediterranean taxon are clearly typical of the genus Chone , therefore, at present, it has been assigned to this genus.

After the first record in the North Tyrrhenian Sea (Gulf of Follonica), the same taxon was found at different sites along the Italian coasts. All the material agrees with the present description, except for that from Fiumicino, which has a higher number of abdominal uncini.

Habitat

Shallow sandy habitats.

Figures

Figure 7. Comparison of thoracic uncini structure in some related sabellin genera having long handle. (A) Type 1 (from Chone duneri); (B) type 2 (from Chone sp.); (C) type 3 (from Chone americana); (D) type 4 (from Amphicorina armandi); (E) scheme of handle orientation found in uncini of types 1–3; (F) scheme of handle orientation found in uncini of types 2–4; (G) SEM photograph of uncini type 1; (H) SEM photograph of uncini type 2.

Figure 8. Chone sp. (A) Entire worm; (B) lateral view of the anterior end; (C) dorsal view of the anterior end; (D) detail of the internal crown structures; (E) radioles showing the development of palmate membrane; (F) thoracic uncinus; (G) abdominal uncini, first chaetigers on the left, last chaetigers on the right; (H) superior thoracic notochaetae; (I) inferior paleate thoracic notochaetae. dl, dorsal lip.

Figure 9. Chone sp. SEM analysis. (A) Notochaetae from the second chaetiger; (B, C) thoracic uncini from the second chaetiger; (D) abdominal uncini from the third abdominal chaetiger.